Ochratoxin A labelled with 14C or 3H in the phenylalanine moiety

Ochratoxin A is a mycotoxin produced by Aspergillus and Penicillium moulds. The toxin is an amide formed between phenylalanine and the isocoumarin acid ochratoxin α. Ochratoxin A with high specific radioactivity can be obtained, by substitution of the natural phenylalanine for 14C of 3H-labelled phenylalanine. Labelled ochratoxin A was formed by condensation of labelled phenylalanine ethylester with an anhydride derivative of ochratoxin α. The intermediate O-acetyl ochratoxin C was hydrolysed with pig liver esterase and chymotrypsin to afford ochratoxin A. The overall yield of radioactivity was 50%. Specific activities up to 500 Ci/mol and 100 ci/mmol for 14C and 3H respectively were obtained. (author)